Methods for synchronizing the rotating blades of aircraft with the aircraft armament have previously been disclosed in patents which date prior to 1920.
The prior art shows many examples of timing a fixed weapon with the propeller of an aircraft by mechanical means. These means usually included a timing chain or cam which was driven by the drive shaft of the engine. The early methods of synchronization were relatively unsophisticated due to fixed weapons. However, ever changing air warfare of the first world war and the years after dictated that technological improvements be made. These included electrical control systems, multiple weapons and control systems in which the weapons are movable. The first two mentioned improvements were relatively simple in that the systems were merely converted from mechanical to electrical operation or additional timing gears or cams were added for additional weapons. The movable or traversable weapon, however, provided a sophistication hitherto unseen in the art.
As an example, U.S. Pat. No. 1,349,140 issued to Martel et al. discloses a control system for a machine gun. The patent teaches the use of a control member that allows for traversing of the weapon while providing synchronization between weapon, propeller and fixed parts of the aircraft. This provides for aiming of the weapon without changing the course of the aircraft. While the invention has its merits, it is unsuited for adaptation to a helicopter because of the mechanical cooperation between the weapon and the drive shaft of the engine.